1. Field of the Invention
The present invention relates to a temperature sensing device for thin-walled thermoplastic pressure vessels used to contain fluids at high pressures and temperatures. More particularly, the invention relates to a device which provides a highly conductive thermal path between the contents of a thin-walled pressure vessel and the outside of the vessel. It allows temperature sensing, measuring and control devices to make temperature readings of the contents of a thin-walled thermoplastic pressure vessels from outside of the vessel and to quickly detect temperature changes.
2. Description of the Prior Art
Most prior art pressure vessels used to contain fluids at high pressures and temperatures are metal structures. Since metal is an excellent conductor of heat, the temperature of the outer surface of the pressure vessel corresponds to the temperature of the vessel's contents. Therefore, temperature sensing and control devices for these prior art pressure vessels typically make temperature readings by placing sensors directly in contact with the outer wall surface of the vessel.
However, recently, manufacturers of pressure vessels have begun to market an increasing number of non-metallic, thin-walled pressure vessels. These pressure vessels have composite outer shells of continuously wound glass filaments impregnated with a thermosetting resin material and inner liners made out of plastic material. Their side walls are relatively thin and light making them easy to handle and construct.
Although the vessels have relatively thin side walls, the materials used to construct them are poor conductors of heat. Consequently, it requires a long period of time before the temperature of the outer wall surface corresponds to the temperature of the vessel's contents, i.e., the temperature of the vessel's wall does not respond quickly or dynamically to changes in the temperature of the vessel's contents. Therefore, the conventional approach of placing a temperature sensing device directly upon the vessel sidewall does not provide an accurate measure of the vessel's contents. In addition, since the vessel is made of a thermoplastic material, it does not allow easy attachment of temperature sensing devices to its walls.
Attempting to modify the sidewalls of these thin-walled pressure vessels to include a metal portion through which temperature sensing may take place presents significant problems. Metal has a coefficient of thermal expansion different than that of the material used to construct these thin-walled pressure vessels. Thus, the metal portion would expand and contract a different rates, separating from the remaining side wall and resulting in leaks or structural damage. The inventions described in co-pending applications: Ser. No. 822,921, entitled "Pressure Vessel with an Improved Sidewall Structure", and filed on Jan. 24, 1986 (now U.S. Pat. No. 4,619,374); Ser. No. 885,300, entitled "A Pressure Vessel with an Improved Sidewall Structure" and filed July 14, 1986; and Ser. No. 885,299, entitled "Method of Manufacturing a Pressure Vessel with an Improved Sidewall Structure" and filed July 14, 1986, all assigned to the assignee of the present application, have overcome these specific problems.
The temperature sensing device of the present invention avoids these problems and allows quick and efficient sensing of the temperature of the pressure vessel's contents. Moreover, it does not contact directly the outer surface of the sidewalls of a thin-walled pressure vessel, thereby avoiding any problems of attachment.
The temperature sensing device of the present invention responds quickly to temperature changes of the contents within a thin-walled pressure vessel. It comprises a member of high thermal conductivity, including an insert segment for placing into a pressure vessel through a port in the shell of the pressure vessel to make contact with the fluid in the vessel, a linking segment disposed in the port of the pressure vessel and an outer plate segment disposed outside of the pressure vessel. Temperature sensing and control devices mounted directly on this outer plate segment take temperature readings of the plate, and accordingly of the vessel's contents.